This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We previously showed that removal of an N-linked glycan, at amino acid residue 197 in the stem of the V2 loop, resulted in increased susceptibility of the mutant virus to broadly neutralizing MAb, and the acquisition of CD4-independent phenotype. Importantly, immunization of pig-tailed macaques with the mutant N7 Env resulted in enhanced neutralizing antibody response not only against the homologous virus, 89.6, but also HIV-1 SF162 and a standard panel of subtype B primary isolates. After intrarectal challenge with SHIV89.6P, immunized animals showed significant reduction of viral load and maintenance of peripheral blood CD4+ T-cells compared to control animals. In this study, we aimed to extend these studies to evaluate the protective efficacy of N7 Env vaccines against a heterologous CCR5 virus challenge.